The previously reported uranium(III) complex [(((ArO)-Ar-Ad)(3)N)U-III(DME)] (1; Ad = adamantane, DME = 1,2-dimethoxyethane) reacts with the terminal bis-alkynes 1,7-octadiyne or 1,6-heptadiyne in C-C-coupling reactions to form the uranium(IV) vinyl complexes [{(((ArO)-Ar-Ad)(3)N)U-IV}(2)(mu-eta(2):eta(1)-1,2(CH)(2)-cyclohexane)] (2) and [{(((ArO)-Ar-Ad)(3)N)U-IV}(2)(mu-eta(2):eta(2)-1,2-(CH)(2)-cyclopentane)] (3). With the monoalkynes 1-hexyne or 4-(t)butyl-phenylacetylene, the complexes [{(((ArO)-Ar-Ad)(3)N)U-IV}(2)(mu-eta(2)(C1):eta(1)(C4)-2-Bu-n-1,3-octadiene)] (4) and [{((AdArO(3)N)UIV}(2)(mu-eta(2)(C4):eta(1)(C1)-1,3-di-(p-Bu-t-phenyl)butadiene))] (5), are formed. These are the first four examples of uranium vinyl complexes that are reported and crystallographically characterized. In addition, detailed DFT calculations are presented to establish a possible mechanism for their formation and explain the differences found for the coordination of the hydrocarbon fragments. In contrast to a previously proposed monometallic pathway for catalytic hydroamination of alkynes and alkyne dimerization involving a uranium vinyl intermediate at uranium(III) complexes, the calculations clearly support a bimetallic mechanism, since its transition states are energetically the most favored.